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UNITED STATES ATnNT much.

NATI-IAN P. STEVENS, OF CONCORD, NEW HAMPSHIRE.

BOILER.

srncrnrcn'rrot forming part of Letters Patent No. 691,200, dated January 14, 1902A Application fled July 20, 1901.

To @ZZ whom t may concern:

Be it known that I, NATHAN P. STEVENS, a citizen of the United States, residing at Concord, in the county of Merrimack and State of New Hampshire, have invented an Improvement in Boilers, of which the following description, in connection with the accompanying drawings, is a specification, like numerals on the drawings representing like parts.

Thisinvention has forits object the production of a novel form of boiler which is not only simple and inexpensive to manufacture, but which has greater heating capacity than boilers as ordinarily constructed.

With this object in view my improved boiler comprises an outer shell and an inner shell inclosed therein and spaced therefrom to form a water-chamber between the two shells. The inner shell forms the fire-box and the combustion-chamber, and extending longitudinally through the inner shell and communieating at their ends with the water-space between the shells are a plurality of elliptical water-chambers. The upper side of the inner shell is preferably attened to form the crownsheet, and such crown-sheet may, if desired, extend the entire length of the boiler instead v of merely the length of the fire-box, as in ordinary horizontal boilers. Since the crownsheet, which is the best steam-producing surface in the boiler, extends the full length of the boiler, it will be seen that I have greatly increased the efficiency of my boiler over the ordinary type of boiler.

Referring to the drawings, Figure 1 is a vertical longitudinal section of a horizontal boiler embodying my invention; and Fig. 2 is a vertical section on the line 2 2, Fig. 1.

I have herein illustrated my invention as applied to the horizontal type of boiler; but I do not wish to limit my invention to this class of boiler.

The outer shell 3 is shown as cylindrical at one end and as having the depending portion 4 at the other end, and said outer shell incloses an inner shell 5, which is smaller than the outer shell and is spaced therefrom to form the annular water-chamber 6, which includes the water-leg 7 between the depending portion 4 of the outer shell and the depending portion 8 of the inner shell. The depending portions 4 and 8 ot' the two shells are connect- Serial No. 69,038. (No model ed together at their lower ends by means of a suitable ring 30, which is of a suitable shape to fit the contour of the Water-leg 7` and of a size to lit the space between the depending portions 4 and 8.

The chamber 9, formed by the depending portion 8 of the inner shell, will have therein the usual grate-bars and will constitute the fine-box of the furnace, while the cylindrical portion 10 of the inner shell constitutes the combustion-chamber, and to provide for the escape of the products of combustion from the combustion-chamber the front end of the inner shell has an opening 12 therein, which communicates with a smoke-collar 1l, extending through the head 13 of the outer casi-ng and into the smoke-chamber 14, which in turn communicates with the usual smoke-stack 15.

Extending longitudinally through the combustion-chamber 10 are a plurality of watertubes or tubular shells 18, which are preferably ilattened or elliptical in shape and which form,in effect, elliptical water-chambers, as seen in Fig. 2, the said water-chambers having their longer diameters substantially vertical and being vertically arranged side by side to form a single transverse row. (See Fig. 2.) Preferably the upper sides of the water-chambers 18 will have communication with the upper space 19 of the Water-chamber through one or more tubes 20.

The upper side 21 of the inner shell is flattened, as shown in Fig. 2, thus forming the crown-sheet of the combustion-chamber, and said attened portion or crown-sheet extends the full length of the boiler, thus, in effect, making a boiler with a crown-sheet extending the full length thereof.

Practice has demonstrated that the crownsheet of the boiler is the best steam-generating surface in the boiler, and by constructing a boiler with a crown -sheet having a largelyincreased area I have provided a boiler which is capable of rapidly and economically generating steam. Furthermore, because of the peculiar shape of the water chambers or compartments 18 and because of their extending longitudinally through the combustion-chamber and receiving the full effect of the heat generated I have provided a boiler with a very large heating-surface.

It will be seen from the above description IOO ' under the steam-pressure generated, I conneet the two shells'by means of a plurality of stay-bolts 25, the said stay-bolts preferably being arranged in rows and staggered. As many stay-bolts may be used as is necessary to properly strengthen the boiler, and the said stay-bolts may be put in place in any suitable way, as by screwing them through the two shells in the boiler or by riveting them in place. The stay-bolts underneath the dome 24 of the outer shell will have their upper ends iiattened to make a foot 26, which is riveted or otherwise secured to the dome, the other end of the stay-bolts being passed through and connected to the inner shell in any suitable way.

In order to construct a boiler which is easy of manufacture, I preferably make the heads at the ends of the shells of a size to slip inside of the shells and provide saidv heads with outturned anges, which can be riveted to the shells from the exterior thereof.

In constructing the boiler the inner shell will preferably first be slipped into the outer shell and the stay-bolts 25 inserted to unite the shells. Since the shells are both open at each end and since the water-chambers 18 are not at this time in the -inner shell, it will be seen that the stay-bolts may be readily inserted and riveted, if desired. The water-chambers l8,which willbe made of the proper shape `and length,will have angle-iron iian ges 3l, riveted to their ends, as shown, and these flanges are then riveted to the front and rear heads 32 and 33 of the inner shell, and the series of water-chambers, with the heads riveted thereto, are slipped into the inner shell from the left-hand end, Fig. 1, the size of the head 32 being such as to admit of this operation. When the heads and water-chambers are in place in the inner shell, the outturned ianges 34 on the head 32 will be riveted to the shell 5, the construction of the head enabling this tobe done from the outside of the shell, as will be obvious, and the outturned flanges 35 on the head 33.will be similarly rivetedto the shell. The smoke-collar 11 may also be riveted to the outturned flange surrounding the opening I2 in the head 32, and the neck 23 will be riveted to the outturned flange 38, surrounding an opening in the head 33, and when this is done the heads 13 and 13 may be slipped into the ends of the outer shell and riveted in place, the outturned anges 3S on said heads permitting this to be done from the outside of the boiler. At the same time the smoke-collar 1l and the neck 23, which project through the headsto the outer shell, will be riveted to the outturned ianges thereon, the said neck 23 furnishing the opening into the lire-box, through which the fuel is introduced.

It will thus be seen that I have constructed a boiler which has a large heating-surface and which can be easily and expeditiously manufactured. If desired, I may pass staybolts, as 40, through the water tubes or chambers 18 in order to'strengthen the same, and I may further use hollow stay-bolts 4l between adjacentfwater-chambers, the hollow stay-bolts operating both to strengthen the structure and to allow communication from one water-chamber to the other. t

Preferably the heads 13 13 of the outer shell will be provided with suitable plugs 43, whichmay be removed when it is `desired to clean the water-chambers, and the depending portion 4 of the outer shell will also be provided with suitable plugs 44, which when removed furnish access to the water-leg to clean the same. v

45 designates auxiliary flues connecting the combustion chamber with the smokechamber 14 on each side of the row of watertubes, such auxiliary flues allowing the products of combustion to escape from the combustion-chamber in case the smoke-collar ll does not allow of sufficient draft.

While I have illustrated one embodiment of my invention, yet I desire to have it understood that various changes may be made in the structure of the device without de- IOO parting from the spirit of the invention expressed in the following claims.

Having described my invention, what I claim as new, and desire to secure by Letters Patent, is-

1. In a boiler, an outer shell, an inner shell inclosed therein and spaced therefrom to form an annular water chamber between said shells, said inner shell containing a fire-box and comprising a combustion-chamber and a plurality of water-chambers extending longitudinally through the inner shell and connecting the water-spaces at the ends thereof, said chambers having a substantially elliptical cross-sectioual area and being situated side by side in a single transverse row.

2. In a boiler, an outer shell, an inner shell inclosed therein and spaced therefrom to form an annular water-chamber, said inner shell comprising the combustion-chamber, -st-aybolts uniting said shells, and a single transverse row of water-chambers extending longitudinally of the inner shell and connecting the water-spaces at the ends thereof, said chambers being substantially ellipticalin cross-section and having their longer diameters substantially vertical.

3. In a boiler, an outer shell, an inner shell inclosed therein and spaced therefrom to form IIQ an annular water chamber between said shells, said inner shell containing a fire-box and constituting a combustion-chamber, and a plurality of tubular shells extending longitudinally through the inner shell and forming water-chambers which connect the waterspaces at the ends of said inner shell, said tubular shells having anges on their ends which are riveted to the heads of said inner shell.

4. In a boiler, an outer shell, an inner shell inclosed therein and spaced therefrom to form an annular water chamber between the shells, said inner shell constituting the combustion-chamber and the upper side thereof being iattened and forminga crown-sheet extending the length of the boiler whereby the heating-surface is increased, combined with a single transverse row of water-chambers eX- their longer diameters substantially vertical:

5. In a boiler, an outer shell, an inner shell inclosed therein and spaced therefrom to form an annular water chamber between said shells, each of said shells having heads set into the ends thereof and provided with outturned flanges which are riveted to the shell, said inner shell constituting a combustionchamber and having a plurality of elliptical water-tubes extending longitudinally there of, said tubes having their longer diameters in a substantially vertical plane.

6. In a boiler, an outer shell, an inner shell inclosed therein and spaced therefrom to form an annular water chamber between said shells, a single transverse row of tubular shells extending longitudinally through the inner shell and forming a plurality of enlarged water chambers which connect the waterspaees at the ends of said inner shell,said shells each having its longer diameter substantially vertical.

In testimony' whereof I have signed my name to this specification in the presence of two subscribing witnesses.

NATI-IAN I. STEVENS.

Witnesses:

ALVIN B. CRoss, HENRY M. BUNKER. 

